1. Field of the Invention
The invention relates generally to hardfacing to enhance resistance to erosion, abrasive wear, and frictional wear. More particularly, the invention relates to high thermally conductive hardfacing for use with drilling equipment and bearings.
2. Background of the Technology
Oil and gas wells can be formed by rotary drilling processes that involve a drill bit connected onto the lower end of a drill string. The drill bit is rotated downhole by rotating the drill string at the surface, actuation of downhole motors or turbines, or both. With weight applied to the drill string, the rotating drill bit engages the earthen formation and proceeds to form a borehole along a predetermined path toward a target zone.
While the bit is rotated, drilling fluid is pumped through the drill string and directed out of the face of the drill bit. The drilling fluid, also referred to as mud, performs several important functions. In particular, the fluid removes formation cuttings from the bit's cutting structure, removes cut formation materials from the bottom of the hole, and removes heat caused by contact between the bit and the formation. The drilling fluid and cuttings removed from the bit face and from the bottom of the hole are forced from the bottom of the borehole to the surface through the annulus between the drill string and the borehole sidewall.
One basic type of drill bit in general use for drilling a wellbore are rotary cone bits, which can also be referred to as rolling cutter bits, milled tooth bits, or rock bits. These generally use one or more rolling cones containing projections called cutting teeth. The cones are rotatably mounted on a drill bit body such that when the drill bit body is rotated and weight is applied, the teeth engage the formation being drilled and the cones rotate, imparting a boring action that forms the wellbore.
Another basic type of drill bit in general use is fixed cutter drill bits which can also be referred to as drag bits. A fixed cutter drill bit uses cutting elements that are attached to a drill bit body. When the fixed cutter drill bit is rotated and weight applied, the cutting elements contact the formation being drilled in a shearing action that breaks off pieces of the formation and forms the wellbore.
Certain surfaces of both rock bits and drag bits as well as other drilling related tools such as reamers, V-stab and stabilizers can be subject to wear during the drilling process, such as the side surface of a bit body that is contact with the wellbore wall and surface areas between the cutting elements of a drag bit. These surfaces may include a layer of material, often referred to as hardfacing or hardmetal, that is designed to resist wear.
Conventional hardmetal materials used to provide wear resistance to the underlying substrate of the drill bit typically comprise carbides. The carbide materials are used to impart properties of wear resistance and fracture resistance to the bit. Conventional hardmetal materials useful for forming a hardfaced layer can also include one or more alloys to provide desired physical properties.
Conventional hardfacing is applied onto the underlying bit surface by known welding methods or thermal spray techniques, such as Laser Cladding, Plasma Transferred Arc or Flame Spray techniques. The associated thermal impact of these processes can cause thermal stress and cracking to develop in the hardfacing material microstructure, which may lead to premature chipping, flaking, fracturing, and ultimately failure of the hardfacing layer. In addition, the process of welding the hardmetal materials onto the underlying substrate can make it difficult to provide a hardfaced layer having a consistent coating thickness, which can negatively impact the service life of the bit.
Accordingly, there remains a need in the art for a wear and fracture resistant hardfacing and hardmetal compositions that experience reduced stress and associated cracking from thermal loading. Such compositions would be particularly well-received if they offered the potential to improve dimensional consistency and accuracy during deposition.